Working in partnership with London TravelWatch

Open windows better than air conditioning on public transport, say passengers

02 March 2021

Passengers see open windows as the most effective method of ventilation for reducing Covid-19 transmission on buses and trains.

Our latest Transport User Community report asked bus and rail passengers about the role ventilation plays in helping them to feel safe when travelling, either now or in the future. It looked at the value of open windows and air conditioning systems.

The research shows that there is high recognition of the importance of ventilation. It is seen to help mitigate against lapses in other areas like social distancing and cleanliness. The communities understand that the virus transmits far less easily outdoors and ventilation is seen as a way to apply this principle to public transport.

Open windows emerged as a clear first preference in the feedback from the communities. Gaps in knowledge exist around what air conditioning can do. Many assume it simply circulates existing air and does little to reduce the spread of droplets throughout the train or bus. Opening a window to let in fresh air is visible and within the passenger’s control, while people can’t see air conditioning working so tend not to trust it.

“I do not know much about the capabilities of air-conditioning systems on trains… If the systems are capable of filtering the air or circulating clean air in, as the inside air is taken out then that has to be great. If, as I suspect, the systems cannot do this but just circulate the same air and control the temperature then opening windows has to be better.” Male, 64, South West (Rail)

When shown examples of best practice, bus passengers felt that an onboard air filtration system sounded impressive. Many would be pleased to see a system like this being used on the buses they use. However, fears around “blowing dirty air around” persisted. Air filtration can only be an extra enhanced safety measure, not replace the need for open windows.

“I think to have these filters would be a great help and reassurance to people but I still don’t think you can beat windows open with proper fresh air. If the air filters are proven to work then I would definitely tell people about it on social media.” Male, 53, South East (Bus)

Likewise, rail passengers thought an advanced air conditioning system which can filter the air and replace it with fresh air from outside sounded good in theory. It was an improvement on many people’s preconceptions that air conditioning recirculates the same ‘stale’ air. Despite this, there was still some doubt about whether it would be as good in practice as is claimed.

“The idea of this sounds amazing however I am hesitant as to the reliability and truth of what I’m reading… For example does this require an expensive filter, how often does it need to be changed? What is the assurance that this system will be maintained? Overall I think I trust windows more.” Female, 30, South East (Rail)

The findings from the research show that while passengers have got the message about the role of ventilation in reducing the spread of the virus, they still need to be convinced about the value of air conditioning or filtration. Transport companies must work harder to plug this gap in understanding and provide more reassurance.

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